• Component Description
• Eligible Sample
• Description of Laboratory Methodology
• Laboratory Method Files
• Laboratory Quality Assurance and Monitoring
• Data Processing and Editing
• Analytic Notes
• References
• Codebook
  • SEQN - Respondent sequence number
  • LBXHIVC - HIV-1, 2 Combo Test
  • LBXHIV1 - HIV-1
  • LBXHIV2 - HIV-2
  • LBXHNAT - HIV Confirmatory Test

National Health and Nutrition Examination Survey

2017-March 2020 Data Documentation, Codebook, and Frequencies

HIV Antibody Test (P_HIV_R)

RDC Only Data File: P_HIV_R.xpt

First Published: July 2021

Last Revised: NA

Due to disclosure issues, this dataset is not available publicly. Access may be obtained through the NCHS Research Data Center (https://www.cdc.gov/rdc).

Component Description

The NHANES program suspended field operations in March 2020 due to the coronavirus disease 2019 (COVID-19) pandemic. As a result, data collection for the NHANES 2019-2020 cycle was not completed and the collected data are not nationally representative. Therefore, data collected from 2019 to March 2020 were combined with data from the NHANES 2017-2018 cycle to form a nationally representative sample of NHANES 2017-March 2020 pre-pandemic data. These data are available to the public. Please refer to the Analytic Notes section for more details on the use of the data.

The estimated prevalence of human immunodeficiency virus (HIV) infection in the United States population is an important measure of the extent of the medical and financial burden the nation faces due to this virus. The current NHANES (1999-present) and HIV antibody data from NHANES III (1988–94) serves as a baseline for monitoring the changes in the epidemic over time in the general population of the United States.

Eligible Sample

Examined participants aged 18–59 years, in the NHANES 2017-March 2020 pre-pandemic sample, were eligible.

Description of Laboratory Methodology

HIV serological and molecular blood test results:

Specimens are initially tested using the GS Combo Ag/Ab Enzyme Immunoassay (EIA) (Bio-Rad Laboratories, Redmond, WA) test method. This test detects simultaneously HIV-1 p24 antigen and antibodies to HIV-1, both groups M and O, and HIV-2. Any specimen that is initially reactive in the screening test is retested in duplicate with the same test. Initially reactive specimens that are reactive in either or both of the duplicates in the repeat testing are referred to as “repeatedly reactive.” Repeatedly reactive specimens are tested with the Bio-Rad Geenius HIV-1/2 Supplemental assay, which both detects and differentiates antibodies to HIV-1 and HIV-2. Geenius results that are antibody-negative or indeterminate and cannot be differentiated as HIV-1 or HIV-2 are further tested using the Hologic Aptima HIV-1 RNA Qualitative Assay to confirm HIV-1 infection.

Refer to the Laboratory Method Files section for a detailed description of the laboratory methods used.

Laboratory Method Files

HIV Combo Laboratory Procedure Manual (February 2020)

HIV Multispot Laboratory Procedure Manual (February 2020)

HIV NAT Laboratory Procedure Manual (February 2020)

HIV Multispot Laboratory Procedure Manual (December 2020)

HIV Combo Laboratory Procedure Manual (December 2020)

HIV NAT Laboratory Procedure Manual (December 2020)

Laboratory Quality Assurance and Monitoring

Serum specimens were processed, stored, and shipped to the Laboratory Branch, Division of HIV/AIDS Prevention , National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention (NCHHSTP), Centers for Disease Control and Prevention, Atlanta, GA for analysis.

Detailed instructions for specimen collection and processing are discussed in the NHANES 2017-2018 and 2019-2020 Laboratory Procedures Manuals (LPMs). Vials are stored under appropriate frozen (–30°C) conditions until they are shipped to the Division of HIV/AIDS Prevention for testing.

The NHANES quality assurance and quality control (QA/QC) protocols meet the 1988 Clinical Laboratory Improvement Act mandates. Detailed QA/QC instructions are discussed in the NHANES LPMs.

Mobile Examination Centers (MECs)

Laboratory team performance is monitored using several techniques. NCHS and contract consultants use a structured competency assessment evaluation during visits to evaluate both the quality of the laboratory work and the QC procedures. Each laboratory staff member is observed for equipment operation, specimen collection and preparation; testing procedures and constructive feedback are given to each staff member. Formal retraining sessions are conducted annually to ensure that required skill levels were maintained.

Analytical Laboratories

NHANES uses several methods to monitor the quality of the analyses performed by the contract laboratories. In the MEC, these methods include performing blind split samples collected on “dry run” sessions. In addition, contract laboratories randomly perform repeat testing on 2% of all specimens.

NCHS developed and distributed a QC protocol for all CDC and contract laboratories, which outlined the use of Westgard rules (Westgard, et al. 1981) when testing NHANES samples. Progress reports containing any problems encountered during shipping or receipt of specimens, summary statistics for each control pool, QC graphs, instrument calibration, reagents, and any special considerations are submitted to NCHS quarterly. The reports are reviewed for trends or shifts in the data. The laboratories are required to explain any identified areas of concern.

Data Processing and Editing

The data were reviewed. Incomplete data or improbable values were returned to the performing laboratory for confirmation.

Analytic Notes

The COVID-19 pandemic required suspension of NHANES 2019-2020 field operations in March 2020 after data were collected in 18 of the 30 survey locations in the 2019-2020 sample. Data collection was cancelled for the remaining 12 locations. Because the collected data from 18 locations were not nationally representative, these data were combined with data from the previous cycle (2017-2018) to create a 2017-March 2020 pre-pandemic data file. A special weighting process was applied to the 2017-March 2020 pre-pandemic data file. The resulting sample weights in the present file should be used to calculate estimates from the combined cycles. These sample weights are not appropriate for independent analyses of the 2019-2020 data and will not yield nationally representative results for either the 2017-2018 data alone or the 2019-March 2020 data alone. Please refer to the NHANES website for additional information for the NHANES 2017-March 2020 pre-pandemic data, and for the previous 2017-2018 public use data file with specific weights for that 2-year cycle.

Refer to the 2017-2018 and 2019 - 2020 Laboratory Data Overview documents for general information on NHANES laboratory data.

There are over 800 laboratory tests performed on NHANES participants. However, not all participants provided biospecimens or enough volume for all the tests to be performed. The specimen availability can also vary by age or other population characteristics. For example, in 2017-March 2020, approximately 76% of children aged 1-17 years who were examined in the MEC provided a blood specimen through phlebotomy, while 95% of examined adults age 18 and older provided a blood specimen. Analysts should evaluate the extent of missing data in the dataset related to the outcome of interest as well as any predictor variables used in the analyses to determine whether additional re-weighting for item non-response is necessary.

Please refer to the NHANES Analytic Guidelines and the on-line NHANES Tutorial for further details on the use of sample weights and other analytic issues.

Demographic and Other Related Variables

The analysis of NHANES laboratory data must be conducted using the appropriate survey design and demographic variables. The NHANES 2017-March 2020 Demographics File contains demographic data, health indicators, and other related information collected during household interviews as well as the sample design variables. The recommended procedure for variance estimation requires use of stratum and PSU variables (SDMVSTRA and SDMVPSU, respectively) in the demographic data file.

The 2017-March 2020 Pre-pandemic Fasting Questionnaire File includes auxiliary information, such as fasting status, length of fast, and the time of venipuncture.

This laboratory data file can be linked to the other NHANES data files using the unique survey participant identifier (i.e., SEQN).

Detection Limits

Since this data is reported as qualitative data, the use of lower limit of detection (LLOD) isn’t applicable.

References

• Bio-Rad Laboratories. Product package insert. GS Combo Ag/Ab EIA. Available at: http://www.fda.gov/downloads/BiologicsBloodVaccines/BloodBloodProducts/ApprovedProducts/PremarketApprovalsPMAs/UCM266211.pdf
• Westgard J.O., Barry P.L., Hunt M.R., Groth T. A multi-rule Shewhart chart for quality control in clinical chemistry. Clin Chem (1981) 27:493-501.

Codebook and Frequencies